In search of the perfect battery

In search of the perfect battery

Mar 6th 2008
From The Economist print edition
Energy technology: Researchers are desperate to find a modern-day philosopher's stone: the battery technology that will make electric cars practical. Here is a brief history of their quest

WHEN General Motors (GM) launched the EV1, a sleek electric vehicle, with much fanfare in 1996, it was supposed to herald a revolution: the start of the modern mass-production of electric cars. At the heart of the two-seater sat a massive 533kg lead-acid battery, providing the EV1 with a range of about 110km (70 miles). Many people who leased the car were enthusiastic, but its limited range, and the fact that it took many hours to recharge, among other reasons, convinced GM and other carmakers that had launched all-electric models to abandon their efforts a few years later.

Yet today about a dozen firms are once again developing all-electric or plug-in hybrid vehicles capable of running on batteries for short trips (and, in the case of plug-in hybrids, firing up an internal-combustion engine for longer trips). Toyota's popular Prius hybrid, by contrast, can travel less than a mile on battery power alone. Tesla Motors of San Carlos, California, recently delivered its first Roadster, an all-electric two-seater with a 450kg battery pack and a range of 350km (220 miles) between charges. And both Toyota and GM hope to start selling plug-in hybrids as soon as 2010.

So what has changed? Aside from growing concern about climate change and a surge in the oil price, the big difference is that battery technology is getting a lot better. Rechargeable lithium-ion batteries, which helped to make the mobile-phone revolution possible in the past decade, are now expected to power the increasing electrification of the car. “They are clearly the next step,” says Mary Ann Wright, the boss of Johnson Controls-Saft Advanced Power Solutions, a joint venture that recently opened a factory in France to produce lithium-ion batteries for hybrid vehicles.

According to Menahem Anderman, a consultant based in California who specialises in the automotive-battery market, more money is being spent on research into lithium-ion batteries than all other battery chemistries combined. A big market awaits the firms that manage to adapt lithium-ion batteries for cars. Between now and 2015, Dr Anderman estimates, the worldwide market for hybrid-vehicle batteries will more than triple, to $2.3 billion. Lithium-ion batteries, the first of which should appear in hybrid cars in 2009, could make up as much as half of that, he predicts.

Compared with other types of rechargeable-battery chemistry, the lithium-ion approach has many advantages. Besides being light, it does not suffer from any memory effect, which is the loss in capacity when a battery is recharged without being fully depleted. Once in mass production, large-scale lithium-ion technology is expected to become cheaper than its closest rival, the nickel-metal-hydride battery, which is found in the Prius and most other hybrid cars.

Still, the success of the lithium-ion battery is not assured. Its biggest weakness is probably its tendency to become unstable if it is overheated, overcharged or punctured. In 2006 Sony, a Japanese electronics giant, had to recall several million laptop batteries because of a manufacturing defect that caused some batteries to burst into flames. A faulty car battery which contains many times more stored energy could trigger a huge explosion—something no car company could afford. Performance, durability and tight costs for cars are also much more stringent than for small electronic devices. So the quest is under way for the refinements and improvements that will bring lithium-ion batteries up to scratch—and lead to their presence in millions of cars.

Alessandro Volta, an Italian physicist, invented the first battery in 1800. Since then a lot of new types have been developed, though all are based on the same principle: they exploit chemical reactions between different materials to store and deliver electrical energy.

A battery is made up of one or more cells. Each cell consists of a negative electrode and a positive electrode kept apart by a separator soaked in a conductive electrolyte that allows ions, but not electrons, to travel between them. When a battery is connected to a load, a chemical reaction begins. As positively charged ions travel from the negative to the positive electrode through the electrolyte, a proportional number of negatively charged electrons must make the same journey through an external circuit, resulting in an electric current that does useful work.

Some batteries are based on an underlying chemical reaction that can be reversed. Such rechargeable batteries have an advantage, because they can be restored to their charged state by reversing the direction of the current flow that occurred during discharging. They can thus be reused hundreds or thousands of times. According to Joe Iorillo, an analyst at the Freedonia Group, rechargeable batteries make up almost two-thirds of the world's $56 billion battery market. Four different chemical reactions dominate the industry—each of which has pros and cons when it comes to utility, durability, cost, safety and performance.

The first rechargeable battery, the lead-acid battery, was invented in 1859 by Gaston Planté, a French physicist. The electrification of Europe and America in the late 19th century sparked the use of storage batteries for telegraphy, portable electric-lighting systems and back-up power. But the biggest market was probably electric cars. At the turn of the century battery-powered vehicles were a common sight on city streets, because they were quiet and did not emit any noxious fumes. But electric cars could not compete on range. In 1912 the electric self-starter, which replaced cranking by hand, meant that cars with internal-combustion engines left electric cars in the dust.

Nickel-cadmium cells came along around 1900 and were used in situations where more power was needed. As with lead-acid batteries, nickel-cadmium cells had a tendency to produce gases while in use, especially when being overcharged. In the late 1940s Georg Neumann, a German engineer, succeeded in fine-tuning the battery's chemistry to avoid this problem, making a sealed version possible. It started to become more widely available in the 1960s, powering devices such as electric razors and toothbrushes.

For most of the 20th century lead-acid and nickel-cadmium cells dominated the rechargeable-battery market, and both are still in use today. Although they cannot store as much energy for a given weight or volume as newer technologies, they can be extremely cost-effective. Small lead-acid battery packs provide short bursts of power to starter motors in virtually all cars; they are also used in large back-up power systems, and make up about half of the worldwide rechargeable-battery market. Nickel-cadmium batteries are used to provide emergency back-up power on planes and trains.

Time to change the batteries

In the past two decades two new rechargeable-battery types made their commercial debuts. Storing about twice as much energy as a lead-acid battery for a given weight, the nickel-metal-hydride battery appeared on the market in 1989. For much of the 1990s it was the battery of choice for powering portable electronic devices, displacing nickel-cadmium batteries in many applications. Toyota picked nickel-metal-hydride batteries for the new hybrid petrol-electric car it launched in 1997, the Prius.

Nickel-metal-hydride batteries evolved from the nickel-hydrogen batteries used to power satellites. Such batteries are expensive and bulky, since they require high-pressure hydrogen-storage tanks, but they offer high energy-density and last a long time, which makes them well suited for use in space. Nickel-metal-hydride batteries emerged as researchers looked for ways to store hydrogen in a more convenient form: within a hydrogen-absorbing metal alloy. Eventually Stanford Ovshinsky, an American inventor, and his company, now known as ECD Ovonics, succeeded in creating metal-hydride alloys with a disordered structure that improved performance.

Adapting the nickel-metal-hydride battery to the automotive environment was no small feat, since the way batteries have to work in hybrid cars is very different from the way they work in portable devices. Batteries in laptops and mobile phones are engineered to be discharged over the course of several hours or days, and they only need to last a couple of years. Hybrid-car batteries, on the other hand, are expected to work for eight to ten years and must endure hundreds of thousands of partial charge and discharge cycles as they absorb energy from regenerative braking or supply short bursts of power to aid in acceleration.

 Lithium-ion batteries evolved from non-rechargeable lithium batteries, such as those used in watches and hearing aids. One reason lithium is particularly suitable for batteries is that it is the lightest metal, which means a lithium battery of a given weight can store more energy than one based on another metal (such as lead or nickel). Early rechargeable lithium batteries used pure lithium metal as the negative-electrode material, and an “intercalation” compound—a material with a lattice structure that could absorb lithium ions—as the positive electrode.

The problem with this design was that during recharging, the metallic lithium reformed unevenly at the negative electrode, creating spiky structures called “dendrites” that are unstable and reactive, and can pierce the separator and cause an explosion. So today's rechargeable lithium-ion batteries do not contain lithium in metallic form. Instead they use materials with lattice structures for both positive and negative electrodes. As the battery discharges, the lithium ions swim from the negative-electrode lattice to the positive one; during recharging, they swim back again. This to-and-fro approach is called a “rocking chair” design.

The first commercial lithium-ion battery, launched by Sony in 1991, was a rocking-chair design that used cobalt oxide for the positive electrode, and graphite (carbon) for the negative one. In the early 1990s, such batteries had an energy density of about 100 watt-hours per litre. Since then engineers have worked out ways to squeeze more than twice as much energy into a battery of the same size, in particular by reducing the width of the separator and increasing the amount of active electrode materials.

The high energy-density of lithium-ion batteries makes them the best technology for portable devices. According to Christophe Pillot of Avicenne Développement, a market-research firm based in Paris, they account for 70% of the $7 billion market for portable, rechargeable batteries. But not all lithium-ion batteries are alike. The host structures that accept lithium ions can be made using a variety of materials, explains Venkat Srinivasan, a scientist at America's Lawrence Berkeley National Laboratory. The combination of materials determines the characteristics of the battery, including its energy and power density, safety, longevity and cost. Because of this flexibility, researchers hope to develop new electrode materials that can increase the energy density of lithium-ion batteries by a factor of two or more in the future.

The batteries commonly used in today's mobile phones and laptops still use cobalt oxide as the positive electrode. Such batteries are also starting to appear in cars, such as Tesla's Roadster. But since cobalt oxide is so reactive and costly, most experts deem it unsuitable for widespread use in hybrid or electric vehicles.

So researchers are trying other approaches. Some firms, such as Compact Power, based in Troy, Michigan, are developing batteries in which the cobalt is replaced by manganese, a material that is less expensive and more stable at high temperatures. Unfortunately, batteries with manganese-based electrodes store slightly less energy than cobalt-based ones, and also tend to have a shorter life, as manganese starts to dissolve into the electrolyte. But blending manganese with other elements, such as nickel and cobalt, can reduce these problems, says Michael Thackeray, a senior scientist at America's Argonne National Laboratory who holds several patents in this area.

In 1997 John Goodenough and his colleagues at the University of Texas published a paper in which they suggested using a new material for the positive electrode: iron phosphate. It promised to be cheaper, safer and more environmentally friendly than cobalt oxide. There were just two problems: it had a lower energy-density than cobalt oxide and suffered from low conductivity, limiting the rate at which energy could be delivered and stored by the battery. So when Yet-Ming Chiang of the Massachusetts Institute of Technology and his colleagues published a paper in 2002 in which they claimed to have dramatically boosted the material's conductivity by doping it with aluminium, niobium and zirconium, other researchers were impressed—though the exact mechanism that causes the increase in performance has since become the subject of a heated debate.

Dr Chiang's team published another paper in 2004 in which they described a way to increase performance further. Using iron-phosphate particles less than 100 nanometres across—about 100 times smaller than usual—increases the surface area of the electrode and improves the battery's ability to store and deliver energy. But again, the exact mechanism involved is somewhat controversial.

The iron-phosphate technology is being commercialised by several companies, including A123 Systems, co-founded by Dr Chiang, and Phostech Lithium, a Canadian firm that has been granted exclusive rights to manufacture and sell the material based on Dr Goodenough's patents. At the moment the two rivals are competing in the market, but their fate may be decided in court, since they are fighting a patent-infringement battle.

The quest for the perfect battery

Johnson Controls and Saft, which launched a joint venture in 2006, are taking a different approach, in which the positive electrode is made using a nickel-cobalt-aluminium-oxide. John Searle, the company's boss, says batteries made using its approach can last about 15 years. In 2007 Saft announced that Daimler had selected its batteries for use in a hybrid Mercedes saloon, due to go on sale in 2009. Other materials being investigated for use in future lithium-ion batteries include tin alloys and silicon.

Corbis Look, no exhaust pipe

At this point, it is hard to say which lithium-ion variation will prevail. Toyota, which is pursuing its own battery development with Matsushita, will not say which chemistry it favours. GM is also hedging its bets. The company is testing battery packs from both A123 Systems and Compact Power for the Chevy Volt (pictured), a forthcoming plug-in hybrid that will have an all-electric range of 40 miles and a small internal-combustion engine to recharge its battery when necessary. To ensure that the Volt's battery can always supply enough power and meet its targeted 10-year life-span, it will be kept between 30% and 80% charged at all times, says Roland Matthe of GM's energy-storage systems group.

GM hopes to start mass-production of the Volt in late 2010. That is ambitious, since the Volt's viability is dependent on the availability of a suitable battery technology. “It's either going to be a tremendous victory, or a terrible defeat,” says James George, a battery expert based in New Hampshire who has followed the industry for 45 years.

“We've still got a long way to go in terms of getting the ultimate battery,” says Dr Thackeray. Compared with computer chips, which have doubled in performance roughly every two years for decades, batteries have improved very slowly over their 200-year history. But high oil prices and concern over climate change mean there is now more of an incentive than ever for researchers to join the quest for better battery technologies. “It's going to be a journey”, says Ms Wright, “where we're going to be using the gas engine less and less.”

寻找完美电池

寻找完美电池

Translated by socrates 

译者按：这篇文章《第一财经》的张红超也有译稿（http://www.eeworld.com.cn/news/power/200804/article_20747.html），但是他只是部分翻译，我将它全文翻译，有个完整的译文供需要的人参考。

        能源技术：研究者们正竭尽全力以找到现代的哲人石（译者注：哲人石是炼金术的最高境界，参见http://en.wikipedia.org/wiki/Philosopher%27s_Stone）：可以让电动汽车实用化的电池技术。如下是他们的探索简史。

        当通用汽车 ( GM )1996年大张旗鼓地发布 EV1 ——一款圆鼓鼓的电动汽车——时，曾被认为是预示着一次革命：电动汽车现代化大规模生产的开始。在双座位的中央部位，一块533千克重的大铅酸蓄电池为 EV1 提供驾驶110km （70英里）的动力。许多人热心十足地租赁了这种汽车，但是由于它的行程范围有限，充电又要耗费数小时，而且还有其他一些原因，致使数年之后， GM 和其他一些发布过全电动原型车的汽车制造商放弃了他们的努力。

        然而如今，许多厂商重新开始开发全电动车或者外挂式混合动力车，使用可进行短途旅行的电池（另外，对于外挂式混合动力车，内燃发动机可使得行程更长）。相比较而言，TOYOTA 广受欢迎的普锐斯（ Prius ）混合动力车，单纯依靠电池，其行程不过减少1英里。位于加州 San Carlos 的 Tesla 汽车最近上市其第一款 Roadster，这是一款全电动双座车，车上携带的450千克电池足以行程350千米（220英里）之后再充电。

        这到底发生了什么改变，使得人们对电动汽车重新燃起兴趣？除了对全球气候变化的日益忧虑和油价飙升，与过去相比，最大的改变在于，电池技术越来越好了。在过去十年中，可充电的锂离子电池使移动电话革命成为可能；现在则预期可支持汽车的不断电气化。“它们明显是下一波，” Mary Ann Wright 确定，她是 Johnson Controls-Saft 先进动力解决方案公司的老板，这是一家合资企业，该企业最近在法国开设了一家为混合动力车提供锂离子电池的工厂。

       根据加州专门研究汽车电池市场的顾问 Menahem Anderman 所说，大量的资本正投向锂离子电池研究，比其他所有化学电池研究上的耗资都要多。一个大型市场正摆在试图采用锂离子电池装备汽车的厂商面前。从现在到2015年， Anderman 博士估计，世界混合动力车电池市场会扩大超过3倍，达到23亿美元。他预计，锂离子电池——第一个采用该型电池的混合动力车将在2009年出现——可能占据其中的一半市场。

       相比较其他类型的可充电电池的化学原理而言，锂离子技术具有许多优势。除了它比较轻之外，它不受任何记忆效应的影响——电池没有耗竭就充电会导致容量上有损失，这种效应称为记忆效应。一旦大规模生产，大规模应用的锂离子技术成本预计要低于它最接近的竞争对手——镍金属氢化物电池， Prius 和大多数其他电动车均采用后者。

       然而，锂离子电池的成功仍具有不确定性。它最大的缺点可能就是它在过热、过度充电或者刺戳时倾向于不稳定性。2006年， Sony ——日本电子巨人——召回了数百万台笔记本电脑电池，因其制造缺陷可能导致某些电池爆炸起火。而汽车电池携带的能量会多上很多倍，如有缺陷将是大型爆炸——这是任何一家公司都无法承受的事故。汽车[电池]所需的性能、耐用性和低廉成本也会比小型电子器件[电池]要严格得多。因此对电池的精制和改良的探索还在继续，使得锂离子电池达到应用标准——最终目标是出现在数以百万计的汽车内。

       1800年，意大利物理学家 Alessandro Volta 发明了第一块电池。自那以后，已经开发了许多新型电池，但无一例外都是遵从一个原理：它们利用不同物质之间的化学反应以储蓄或者提供电力能源。

回顾电池基础知识

        一个电池通常由一组或多组电池元组成。每个电池元都包括一个正电极和一个负电极，两个电极用一个浸在导电电解液中的隔离器隔开，该电解液允许离子而不是电子在两个电极之间来回传输（译者注：具体参见下面那个电池结构图）。当把电池接到一个负载上，化学反应就开始了。当带正电荷的离子从负电极游过电解液来到正电极，成比例的带负电的电子就从外面电路经历同样的历程，结果是产生了做有用功的电流。

        一些电池是基于一些可逆的化学反应。这种可充电电池的优势在于它可以通过在充电时候发生的电流逆向传导过程将之恢复到带电状态，因此可以成百上千次重复使用。 据 Freedonia Group 的 Joe Iorillo 估算，充电电池占据了世界560亿美元电池市场的三分之二。四种不同的化学反应主导了工业界——当考虑到效用、耐用性、成本、安全性和性能时，它们中的每一种都有优劣之分。

        1859年，法国物理学家 Gaston Planté 发明了可充电电池。在19世纪晚期，欧洲和美国的电气化进程开始将蓄电池大规模用于电信技术、便携式电灯系统和后备电源。但是最大的市场可能是电动汽车。在上世纪之交，电池驱动的汽车成为城市里的街道一景，因为它们行驶安静而且不排放有毒烟气。但1912年，电动自起动器取代手动之后，内燃发动机系统装备的汽车把电动车遥遥甩在身后。

        1900年左右，人们发明了镍镉电池，它最初在需要更多能源的时候使用。如同铅酸电池，镍镉电池在使用时往往会散发出有毒气体，特别是过度充电的时候。1940年代晚期，德国工程师 Georg Neumann 成功地微调了电池的化学机制，从而消除了这个问题，使得将之密封包装成为可能。1960年代，这种技术开始在电动剃须刀和电动牙刷上广泛使用。

        20世纪的大部分时期，铅酸电池和镍镉电池主导了充电电池市场，而且如今仍然在使用。虽然在一定重量和体积下，它们的储能不及新一代技术，但是它们也许是非常符合成本效益的。实际上，所有汽车的起动发动机所需的短脉冲能量都是由小型铅酸电池组提供的；它们也在大型后备电源系统中得到应用；而且它们占据了世界充电电池的大约半壁江山。镍镉电池也用作飞机和火车的应急后备电源。

换电池的时候到了！

        在过去20年中，两种新型充电电池闪亮登场。1989年，市场上出现了在同样重量下储能是铅酸电池两倍之多的镍金属氢化物电池。1990年代的大部分时期，它是便携式电子设备的优选，在许多应用领域取代了镍镉电池。 TOYOTA 为他们在1997年问世的新型混合油-电汽车——Prius——选择了镍金属氢化物电池。

        镍金属氢化物电池从曾用于卫星上的镍氢电池发展而来。这种电池价格昂贵而且体积很大，因其需要高压储氢罐， 但它们提供了很高的能量密度且可持续使用很长时间，因此比较适合在太空中使用。当研究者寻求储氢的更便捷方法——使用可吸收氢的金属合金——时发现了镍金属氢化物电池。最终美国发明家 Stanford Ovshinsky 与他的公司 ECD Ovonics 成功地制备了随机结构的金属氢合金，实现了性能改良。

        在汽车环境中使用镍金属氢化物是不小的进步，电池在混合动力车中的工作方式和在便携式设备中的工作方式非常不同。在笔记本电脑和移动电话中的电池被设计成可在数小时或数天过程中连续使用，且它们只需有数年寿命。然而，混合动力车中的电池，人们希望它能工作8-10年，而且必须承受成百上千次的不完全的充电/放电循环，从再生制动中吸收能量或者在加速时提供短脉冲能量。

        锂离子电池从不可充电的锂电池发展而来，通常锂电池用于手表和助听器中。锂金属特别适于制造电池的一个原因是它是最轻的金属，这意味着相对于同等重量的其他金属（比如铅或镍）而言，锂电池可储存的能量会更多。早期的可充电锂电池使用纯锂金属作为电负极材料，一个“插入式”化合物——该种材料具有的栅格结构可以吸收锂离子——作为电正极。

        这种设计存在的问题是，在充电时，金属锂重新出现在电负极上时其形状不够均匀，而且会生成尖刺状结构，称为“树枝状结构（ dendrites ） ”，这种结构不但不稳定而且易起反应，一旦穿过隔离器就会造成爆炸。所以今天的充电锂离子电池并不采用金属形态的锂元素。取而代之的是在正极和负极上使用栅格结构材料。当电池放电的时候，锂离子从负极栅格游到正极栅格；充电时它们游回来。这种往回式方法称为“摇椅 （ rocking chair ）”式设计。

       1991年， Sony 发布了第一款商用锂离子电池，它采用的就是摇椅式设计，其中用钴氧化物做正极，石墨（ 碳 ）做负极。在1990年代早期，这种电池每升的能量密度是大约100瓦时。从那以后，工程师们通过减小隔离器宽度和增加活性电极材料数量，不断改进锂离子电池工艺，如今其单位能量密度已经翻倍。

       高能量密度的锂离子电池使得它们成为移动设备的最佳技术。根据巴黎市场调查公司 Avicenne Développement 的研究员 Christophe Pillot 所说，锂离子电池在70亿美金的移动式充电电池市场中占据了70%份额。但并非所有的锂离子电池都是相同的。美国劳伦斯伯克利实验室（ Lawrence Berkeley National Laboratory ）的科学家 Venkat Srinivasan 介绍道，容纳锂离子的主体结构可以用许多种材料制成。材料之间的结合决定了电池的特性，包括它的能量和功率密度，以及安全性、使用寿命和成本。因为具有这种弹性，研究者们期待能开发出新的电极材料，未来也许可以把锂离子电池的能量密度提高2倍或以上。

缠上了锂

        如今在移动电话和笔记本电脑中使用的电池通常都是用钴氧化物作为正极。这种电池也开始出现在汽车中，比如 Tesla 开发的 Roadster。但因为钴氧化物是如此的昂贵且易起反应，大多数专家认定它是不适于在混合动力或者全电动汽车中大规模使用的。

        所以研究者们正在试验其他办法。一些公司，比如在密歇根 Troy 的康柏电脑公司，开发了一种用锰取代钴的电池，锰这种材料相对比较廉价而且在高温下更稳定。但不幸的是，使用锰电极的电池储能比钴电极电池相对要少一些，而考虑到锰会融化入电解液中，故其使用寿命也相对较短。但将其他元素，比如镍和钴混入锰中，可以减轻这个问题， Michael Thackeray 说道，他是美国阿拉贡国家实验室（ Argonne National Laboratory  ）的科学家，在此领域拥有数项专利。

        1997年，德克萨斯大学（ University of Texas ）的 John Goodenough  和他的同事发表了一篇论文，其中他们建议使用一种新的正电极材料：磷酸铁 （ iron phosphate ）。相对于钴氧化物而言，它更加低廉，更安全也更环保。只是存在两个问题：它的储能比钴氧化物要低，而且导电率也较低，这限制了电池释放和存储能量的速度。所以当2002年 MIT 的 Yet-Ming Chiang 宣称他们通过在材料中掺杂入铝、铌和锆之后大幅度提高材料的导电性时，其他研究者都留下深刻印象——即便性能提升的机制自那时候起一直是热烈辩论的热点话题。

        2004年 Chiang 博士的小组发表了另外一篇文章，描述了进一步提高性能的办法。使用直径少于100纳米的磷酸铁颗粒——大约比通常所用小100倍——提高电池的表面积，由此可提高电池存储和释放能量的能力。但这次又是一样，其中包含的准确机制仍然众说纷纭。

        目前有数家公司正在商业化磷酸铁技术，包括Chiang 博士参与成立的 A123 Systems 公司，和唯一授权制造和销售基于 Goodenough 博士专利的材料的加拿大公司—— Phostech Lithium 公司。目前这两家公司正在市场上交战，但是他们的命运也许决定于法庭，因为他们正在打一场侵权官司。

完美电池的探求之旅

        2006年，Johnson Controls 和 Saft 成立了一家合资企业，他们采用不同的技术路径，其中正极用镍钴铝氧化物制备。公司老板 John Searle 说采用这种技术的电池可以使用长达约15年。2007年，Saft 宣布，Daimler 已经决定在一种混合动力的奔驰轿车上使用他们的电池，该轿车2009年上市销售。其它正在研究的可用于未来锂离子电池的材料包括锡合金和硅材料。

        目前，很难说哪一种锂离子技术变种会胜出。 TOYOTA 目前正在和 Matsushita 合作开发他们自己的电池技术，他们也难以确认哪一种技术最好。 GM 也在这一领域下赌注。 GM 正在为他们的 Chevy Volt 测试 A123 Systems 和 Compact Power 生产的电池组，这种即将问世的汽车全电动行程是40英里，上面装备一个小型的内燃发动机用于需要时给电池充电。为了保证 Volt 的电池总是能提供足够的动力，以及具有10年的使用寿命，该电池的充电量将一直保持在30%到80%之间， GM 储能系统集团 （ GM's energy-storage systems group ）的 Roland Matthe 说道。

       GM 希望能在2010年晚期大规模生产 Volt。这是野心勃勃的计划，因为 Volt 能否及时问世取决于是否出现适用的电池技术。“要不是巨大的成功，要不败得一塌糊涂，” James George 说，他是新罕布什尔州的电池专家，跟踪电池工业长达45年。

       “就得到完美电池而言，我们还有很长的路要走，” Thackeray 博士说道。在过去数十年中，大约每2年计算机芯片性能就翻倍；但在过去200年历史中，电池的发展非常缓慢。高昂的油价以及对气候变化的忧虑，意味着研究者们将以前所未有的动力去加入追求更好性能的电池技术的行列。“这将是一次旅程，” Wright 小姐说道， “伴随着我们越来越少地使用内燃发动机。”